ECU
One of the major ways gains can be found on modern engines is by reprogramming the ECU to reflect modifications to the engine or to change poor factory programming. There are two general ways to modify the operation of the ECU, one method is to reprogram the information stored in the memory and the other is to modify the input to or from the ECU. Generally, the preferred method of modifying the computer is to change the instructions within the ECU itself; however to do so the instructions in the ECU must typically be de-crypted and reverse engineered in order to make sense of the factory programming, prior to writing a new set of value tables. Finding where the value tables are stored, how they relate to eachother, and how to modify them are all major technical hurdles that are not yet understood for the SX4. While one major aftermarket manufacturer, Cobb Tuning, began the process of reverse engineering the information from the ECU, only little progress was made and they were unable to successful implement their AccessPort re-flashing software. Lucky for us, there are other ways of modifying the engine all of which allow the ECU to continue using stock instructions, while modifying either the inputs or outputs in order to obtain the intended results. The drawback of these systems are the lack of adjustability for sensors and systems which are internal to the ECU, in other words they lack the ability to modify deeper instructions such as throttle sensitivity or fuel trim values, instead they modify the signals sent to or from existing systems outside the ECU. The simples of these modifications is the ever-present "EBay chip," which is designed to fit between the intake air temperature sensor, and the ECU. The "chip" is used to hijack the original IAT signal and change it so that the air appears much cooler than normal, which prompts the ECU to run richer than it would if the sensor read hotter air. Unfortunately, the effect for the SX4 would be the opposite of most cars; since the SX4 already runs rich, it would benefit from running slightly leaner to generate more power (with less margin of safety in the air/fuel ratio). Another method of modifying the ECU signals is by intercepting the signals sent FROM the ECU and modifying them externally in order to change the operation of the engine. Technically speaking, there are a number of products which have the ability to perform these changes to the output, but the three used (so far) on the SX4 are the Split Second PSC-1 and FTC-1 (air/fuel programming and timing + air/fuel programmign respectively) as well as the open source MegaSquirt II (which can replace the majority of ECU functions or operate as a "piggyback" controller). By intercepting and replacing values based on a conversion table, the PSC-1 and FTC-1 allow the factory ECU to operate as normal while changing the values sent to the fuel injectors to modify the amount of fuel. The FTC-1 allows the substitution of ignition tables as well as fuel, for full control of ignition advance and retard. MegaSquirt II is a full function ECU which can also intercept factory outputs and modify them based on tables and other inputs, either fuel, spark, or both. There are also other, similar controllers on the market which SHOULD be capable of interacting with the stock ECU. The Split Second line of controllers has been investigated and implemented by Road Race Motorsports (premier SX4 tuner) and the MegaSquirt line has been used by Turbine Tech (which offers it with their turbo kit). However, there are other controllers which are almost identical in function to both these devices, such as those made by Perfect Power, Apex'i, and HKS. Link to Internal parts of SX4 ECU: www.lockbook.in/article/how-to-open-maruti-suzuki-sx4-ecm-ecu/ http://lockbook.in/article/how-to-open-maruti-suzuki-sx4-ecm-ecu/